The present invention is directed to the beneficiation of complex non-sulfide ores such as fluorspar ores using trifluoromethyl group-containing compounds as selectivity agents.
Fluorspar has wide and varied application in the chemical, ceramic, and metallurgical industries. Its uses range from a source of fluorine and hydrofluoric acid in chemical processes to that of a fluxing material in steel making. Commercial fluorspar, commonly referred to as "spar," is furnished to meet a number of varying specifications as to size and analysis. The fluorspar content of the commercial products ranges from a minimum of 85 percent in the case of "gravel spar" for steel making to a minimum of 97% fluorspar in the "acid grade" material for chemical processing. The specifications as to allowable impurities vary with the industry, but all industry requirements demand a fluorspar product relatively free of silica, calcium carbonate, barite, and sulfides such as galena, sphalerite, or pyrite. Fluorspar ores as mined seldom meet commercial specifications, either with regard to fluorspar content or freedom from impurities, and suitable methods of concentration, such as froth flotation, must therefore be employed to recover commercial products from the low grade or contaminated ores.
Geographically, fluorspar is widely distributed in minute quantities, but deposits of commercial value in the United States are not numerous. Fluorspar deposits occur in both igneous and sedimentary rocks, as veins following faults, fissures or shear zones; as horizontal or bedding replacement deposits in sedimentary rocks; or as incrustations in vugs and caves. Sizable deposits of fluorspar are known in the western states including California, Arizona, New Mexico, Nevada, Texas and Colorado. The vein and bedded deposits in the Illinois-Kentucky area are reputed to be among the largest in the world. The improved process of froth flotation of the present invention can be used for the beneficiation of ores from various localities.
The gangue minerals commonly found associated with fluorspar in commercial deposits are quartz, calcite and barite. Other accessory minerals may include sulfides such as galena, sphalerite, pyrite or chalcopyrite; or oxidized lead and zinc minerals such as cerussite and smithsonite. Common gangue constituents of fluorspar ores are limestone and clay, and many ores also contain shale and sandstone. Ores from different deposits, or from different portions of the same deposit, may show considerable variation both with regard to mineral association and relative proportions of fluorspar and other minerals. In the Illinois-Kentucky fluorspar district, for example, the ore from a particular deposit may be devoid of barite, whereas the ore from an adjacent deposit may contain ten percent or more of barite. Similarly, the galena or sphalerite contents may also show considerable variation. Ore from a particular mine location may contain minute quantities of galena or sphalerite, whereas ore from another part of the mine often contains sufficient galena or sphalerite to justify their recovery as valuable by-products in fluorspar milling. The lime and silica contents of fluorspar ores may likewise show considerable variation. Uniform deposits of fluorspar are an exception rather than the rule, and milling methods must be sufficiently flexible to permit treatment of a variety of ores of different grades and mineral association. An important object of this invention is to provide a flotation method applicable to a variety of ores of different grades and mineral association for recovery of the fluorspar and barite concentrates from associated gangue materials.
Barite, or barium sulfate, is often found in the fluorspar ores, and is the chief source of barium chemicals. Unground crude barite is used for the production of lithopone and barium chemicals. Ground barite, which is sold in numerous sizes and degrees of purity, is used in oil well drilling mud; glass making; as a filler for paper, rubber, oilcloth, linoleum, etc.; paint pigments; X-ray apparatus; storage batteries; and brass smelting.
It is known to use fatty acid and related sulfates and soaps as collection reagents to float fluorspar; however, the separation has been difficult because the fatty acid-type collectors for fluorspar are non-selective and tend to float everything, with the exception of the silica.
It is well known in the art that the sphalerite may be activated with copper sulfate and the sulfides floated with xanthates or dithiophosphates. The slurry, free of sulfides, is then ready for the fluorspar flotation. In order to float the fluorspar with fatty acids, the carbonates and the barite must first be depressed. Methods have been developed in the past to depress the carbonates and the barites by the addition of quebracho, or ligninsulfonate, at a pH between 9 and 10. This treatment, in the case of complex ores, was only partially successful. To enhance a better and cleaner separation, sodium fluoride was added to the flotation medium (U.S. Pat. No. 2,407,641, to Clemmer et al). Later, chromates and dichromates were used to keep the barite down during the fluorspar flotation. Although sodium fluoride increased selectivity in the flotation considerably, sodium fluoride is a poisonous and relatively expensive additive. The use of chromates and dichromates, on the other hand, creates a serious environmental problem from the chromium ion.